Blog 7: Duverger's Law

Blog 7: Duverger’s Law

            According to Maurice Duverger and Gary Cox, the effective number of political parties in a country depends entirely on the electoral rules.  They both support the claim that when electoral rules dictate that when there is one member of the legislature for every district and he or she wins with plurality vote (receiving the most votes, regardless of whether or not it is actually fifty percent) instead of majority vote (over fifty percent) then there will end up being only two effective parties.  However, if the districts each elect multiple members of the legislature and they are chosen through a proportional representation system (a party will receive roughly the same percentage of seats as they do percentage of votes) then there will be more than two effective parties (Shively 231).

            To test Deverger’s Law, I chose to continue my study of Colombia.  Colombia has a bicameral legislature with a Chamber of Representatives and a Senate.  For this study I focused on the Chambor of Representatives which has 164 members elected with a proportional representation system (Wikipedia) and calculated the number of existing effective parties.  To find this number I took the percentages of seats each party won, squared them, found the sum of those numbers, and found one divided by that answer to find that Colombia has 5 effective political parties, which does support Duverger’s Law.

            To find out more, I looked into Colombia’s electoral rules, starting with the district magnitude to find out how many seats were allotted to each electoral district.  The Chamber has 164 seats in total and 33 districts.  I divided the number of seats by the number of districts to find that roughly 5 members of the Chamber were allotted to each district.  However, I also found out that only 2 members are actually assigned to each the district.  The rest depends on population.  The district will receive 1 more representative for every 250,000 more people it has after the first 250,000, so the system favors more heavily populated areas. 

            However, because the percentage of votes cannot match up exactly with the percentage of seats, there must be a formula for calculating who the extra seats go to.  The formula Colombia uses is the largest remainder (IPU Parline Database).  With this method, the percentages are rounded down at first and seats are distributed.  Then the rest of the seats are distributed based on which party has the greatest remainder. For example, if one party receives 25.9% of the vote and another receives 22.3%, the first party would be given 25% of the seats and the other would be given 22%.  Then, if there was one seat left, it would be given to the first party which had a remainder of .9% while the other had a remainder of only .3%.  This method is very efficient at making the distribution as close as it possibly can be. 

            Proportional Representation makes it difficult to have the people vote for individual candidates, most countries that use this system have the people vote for a party.  Each party then has a list of candidates and when it receives the number of seats it is allowed to fill, it simply begins at the top of the list until it has enough candidates to fill the spots it receives.  However, in some countries have a preferential list structure where the people are still allowed to vote for a specific candidate within the party list.  Colombia has a non-preferential list, where the party does not allow the people to vote for specific people within the party list.  Should a vacancy arise in the Chamber between elections, the party simply picks the next person on the list (IPU Parline Database). 

            Because the proportional representation system allows for very small parties to gain a spot, some governments, in order to make the election process more simply, have a threshold where unless a party can receive a certain percentage of the votes, it cannot win any seats in the legislature.  Colombia does not have a threshold.  In 2010, one of the parties only received .1% of the vote and it was still granted one of the seats.  The only way a party cannot get a seat is if it cannot get a percentage of the vote that is high enough to get it a seat (Wikipedia). 

            According to the information calculated and found, Colombia proves Duverger’s Law to be correct.  Single Member District Plurality Systems result in a system with only two effective parties while Proportional Representation Systems result in multiple parties having an effect in the legislature. 

           

           

           

 Works Cited

Colombia: House of Representatives. Inter-Parliamentary Union.  http://ipu.org/parline-e/reports/2067_B.htm. Web. 31 October, 2012.

Elections in Colombia. Wikipedia.  http://en.wikipedia.org/wiki/Elections_in_Colombia. Web. 31 October 2012.

Shively, W. Phillips. Power and Choice: An Introduction to Political Science. New York: McGraw-Hill Companies Inc. 2012